It would be an advanced function of a tactile sensor for being able to verify either the softness or the hardness of a matter, particularly being utilized to identify different portions of an animal's body based on the softness or hardness thereof. However, those tactile sensing apparatuses known to the art are either too complicated or short in performance. These shortages render the currently prevailed tactile sensors hard to be used for identifying physical materials as soft as tissues of human bodies.
Please refer to FIG. 1, which is a schematic diagram illustrating an endoscope 10 capable of verifying the hardness of a tissue. It can be observed from FIG. 1 that, an external structure 12 is disposed at the front end of a traditional endoscope 11 for adapting a spring 13 with an observation window 14 and a filter 15 at the front. The axis of the endoscope 10 lies along the direction of the Z-axis. FIG. 2 shows a cross-sectional view of the spring 13 of the endoscope 10 at a plan A-A illustrated in FIG. 1. Apparently, the endoscope 10 is good for used in analyzing material properties, such as hardness or elastic coefficient, of a matter or a tissue in front of the endoscope 10, by collecting the deformation of the spring 13 due to a force Fz along the direction of Z-axis. However, according to FIG. 2, those external forces at either the direction of X-axis Fx and the direction of Y-axis Fy is not measurable by the endoscope 10. Besides, the effectiveness in terms of determining the degree of hardness for the apparatus illustrated in FIG. 1 is limited, and sometimes causes misjudging.
Some people suggested a method for verifying the mechanical properties of a matter by using the transmission of vibration signals. According to a research resulting with low-frequency vibrations, however, the measurement at low power may easily be disturbed by noises, and the accuracy thereof is insufficient. Some other sensing device for detecting material properties based on different physical concepts are also hard to be used for distinguishing soft materials such as sponge and gelatin.
According to the above-mentioned, there is a need to develop a new method for measuring a material property of a matter to overcome all those deficiencies of the prior arts.